Various approaches for connecting pipes to manholes in sewer systems are known. U.S. Pat. No. 3,958,313 Assigned to NPC, Inc. discusses considerations and complications that are associated with the installation of such sewer systems, particularly with respect to the alignment and sealing of pipes and manholes. This patent proposes a seal in the form of a boot. A first end fits over a pipe; a second end, within a porthole formed in the manhole riser; and a transition section extends between the two ends. During installation hydraulic or other jacking means move links on an expandable ring, placed inside the second end of the seal. The links expand the ring with considerable force and seal the second end of the boot to the riser at the porthole. With the pipe inserted through the first end of the boot, an external clamp seals the second end to the pipe and completes the connection. While this approach is generally effective, complexity in seal manufacture and the requirement for separate clamping members increases the overall costs of the seal and of its installation on site.
Another class of pipe-to-riser seals comprises hollow sealing structures in which filler materials expand the riser. In U.S. Pat. No. 2,815,966 installation requires the steps of filling an annular sleeve with polybutene and then squeezing the sleeve to evacuate the sleeve of air and the polybutene. A film of polybutene remains to keep the internal surfaces of the sleeve together. The collapsed sleeve rests on the spigot end of a pipe which is positioned within the bell portion of an adjacent pipe. A self-hardening cementitious grout, forced into the sleeve, breaks the internal seal formed by the polybutene and expands the sleeve into the space between the spigot and the bell whereupon the grout hardens and maintains the seal. U.S. Pat. No(s). 3,222,076 and 3,258,271 disclose similar seals in which the filler material comprises a liquid that hardens. In accordance with U.S. Pat. No. 3,473,829, a liquid that solidifies in time fills the seal for permanent installations; a gas filler material is used for temporary installations.
U.S. Pat. No. 4,269,419 discloses a double-walled sleeve with ribbed surfaces that contact the pipe and the manhole. After the seal is positioned, an elastomer or other fluid, that is not intended to set up completely, is forced into the sleeve through an input valve under pressure. When the material emerges from a vent valve, the vent valve is closed with a pressure gauge. Additional pumping occurs until a predetermined pressure is achieved at the vent valve whereupon the valves are closed. The material then assumes its final form over time.
Each of the foregoing systems requires special materials or equipment. U.S. Pat. No. 2,815,966 requires the use of polybutene and rollers for a special evacuation step. U.S. Pat. No(s). 3,222,076 and 3,258,271 and 4,269,419 require separate filling and vent valves. U.S. Pat. No. 3,473,829 requires separately extruded or formed components that are connected together to form a seal. These extra or specially formed components add to the cost of the seal itself and to the complexity and cost of on-site installation.
From time-to-time, it has been found that insufficient filler has been forced into the seal, and the seal leaks. In the foregoing proposals, however, the filler materials have either hardened or formed a resilient solid mass before this problem is evident. This makes it difficult to reestablish the seal by introducing more filler, as the hardened or set mass blocks the effective transfer of additional material throughout the sleeve. Thus, in such situations it has been necessary to remove the sleeve from the pipe, often with considerable difficulty and often with excavation around the manhole.